Source is this video:
Windows Was The Problem All Along - Dave2D
We could obviously compare performance between windows and steamOS before on the steam deck, or between windows and Bazzite on other handhelds. But this is the first time we have had official windows and SteamOS builds for the same hardware.
Most people dont use Windows because its compatible with more software, they use it because thats what their computer came with. If computers just starting shipping Linux then software will come.